import java.util.Optional;

/**
 Java 8 Optional 类
     网站：https://www.runoob.com/java/java8-optional-class.html
 */
public class JDK_6 {
    public static void main(String args[]){
        JDK_6 jdk_6 = new JDK_6();
        Integer value1 = null;
        Integer value2 = new Integer(10);

        // Optional.ofNullable - 允许传递为 null 参数
        Optional<Integer> a = Optional.ofNullable(value1);

        // Optional.of - 如果传递的参数是 null，抛出异常 NullPointerException
        Optional<Integer> b = Optional.of(value2);
        System.out.println(jdk_6.sum(a,b));
    }

    public Integer sum(Optional<Integer> a, Optional<Integer> b){
        // Optional.isPresent - 判断值是否存在
        System.out.println("第一个参数值存在: " + a.isPresent());
        System.out.println("第二个参数值存在: " + b.isPresent());

        // Optional.orElse - 如果值存在，返回它，否则返回默认值
        Integer value1 = a.orElse(new Integer(0));

        //Optional.get - 获取值，值需要存在
        Integer value2 = b.get();
        return value1 + value2;
    }
}